In order for most athletes to perform at peak efficiency, they must effectively view their surroundings and circumstances and they typically must quickly and precisely react accordingly. Athletes usually spend hours, days, and months training so as to increase their athletic performance, but they often neglect taking steps to improve their vision and reaction time accordingly.
Known vision improving exercises and methods are typically performed off-field, and usually not during game play. As a result, when athletes are involved in game play and the like, they tend to forget or not use their vision improving techniques, thereby rendering them useless at improving an athlete's performance when it counts most, during the sporting event.
Similarly, many vision training drills and exercises to not use traditional equipment used by an athlete while playing their particular sport.